perf timechart: Fix max number of cpus

Currently numcpus is determined in pid_put_sample which is only
called on sched_switch/sched_wakeup sample processing.

On a machine with a lot cpus I often saw the last cpu missing.

Check for (max) numcpus on every event happening and in the
beginning. -> fixes the issue for me.

Signed-off-by: Thomas Renninger <trenn@suse.de>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: lenb@kernel.org
LKML-Reference: <1298842606-55712-6-git-send-email-trenn@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>